Ricard Garcia-Valls

Modification of ceramic membranes by alcohol adsorption

This study aims at modifying ceramic membranes by means of alcohol chemisorption. Composite ceramic membranes with a skin layer of -alumina were used. First, the adsorption of several alcohol on powdered -alumina was investigated emphasising the thermal stability of the adsorbed compounds. Later, a commercial -alumina membrane was modified by alcohol adsorption. The permeability of water and several organic compounds was obtained for both the non-modified and modified ceramic membrane. Also, its isoelectric point was determined. The results prove that all the alcohol were readily adsorbed on powdered -alumina not only physically but also chemically forming an alkoxide. The chemisorbed alcohol was stable up to 200 ◦ C. Beyond this temperature, the alkoxide breaks up releasing the alcohol although the alkoxide also can react yielding an olefin or ether. The ceramic membrane was also successfully modified by alcohol adsorption. The layer of chemisorbed alcohol imparts hydrophobic characteristics to the membrane surface, so water permeability decreases significantly. This cannot be merely explained by pore size reduction due to the adsorbed layer. Thermal treatment at 250 ◦ C recovered original permeability with only minor damage to the membrane.

Light-induced switching of the wettability of novel asymmetrical poly(vinyl alcohol)-co-ethylene membranes blended with azobenzene polymers.

Novel composite asymmetrical membranes based on poly(vinyl alcohol)-co-ethylene (EVAL) as the host material and new polyethers that contain azobenzene moieties in the side chain were prepared by dry-cast phase inversion after dissolving the azo polymers in tetrahydrofuran and EVAL in dimethylsulfoxide and subsequently mixing the resulting solutions. By taking advantage of the proper temperature variation in the oven used for solvent evaporation, asymmetrical membranes that exhibited a dense, crystalline layer on the bottom and a porous, mainly amorphous layer on the top were obtained. Remarkable changes in the surface morphology and the contact angle with water were observed on the top surfaces of the composite membranes. This was ascribed not only to the enhanced concentration of azo polymer on the top surface but mostly to a conformational change in EVAL induced by the photoisomerization of the guest azo groups, as shown by HRMAS (1)H NMR. The morphological and structural changes in EVAL could be reversed on exposing the membrane to visible light for 24 h.

Characterization of polysulfone and polysulfone/vanillin microcapsules by 1H NMR spectroscopy, solid-state 13C CP/MAS-NMR spectroscopy, and N2 adsorption-desorption analyses.

Textile detergent and softener industries have incorporated perfume microencapsulation technology to improve their products. Perfume encapsulation allows perfume protection until use and provides a long-lasting fragrance release. But, certain industrial microcapsules show low encapsulation capacity and low material stability. Polysulfone capsules have been already proposed to solve these drawbacks. Among them, PSf/Vanillin capsules were considered as a desirable system. They present both good material stability and high encapsulation capacity. However, several factors such as the final location of the perfume in the polymeric matrix, the aggregation state that it has in the capsule and its interaction with the capsule components have not been studied yet. These factors can provide vast information about the capsule performance and its improvement. With the aim to characterize these parameters, the physical and chemical properties of PSf/Vanillin capsules have been investigated by nuclear magnetic resonance (NMR) spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), and N(2) adsorption-desorption measurements. AFM micrograph and N(2) isotherms confirm that the presence of vanillin modify the physical structure of PSf/Vanillin microcapsules as it is trapped in the capsule porosity. NMR results show that vanillin is present in solid state in PSf/Vanillin microcapsules.

Optimizing seawater operating protocols for pressurized ultrafiltration based on advanced cleaning research

Abstract This paper is part of a global research project conducted by Dow Water & Process Solutions to optimize the efficiency of ultrafiltration processes. After an initial identification of the backwash as the key opportunity to increase the efficiency of the process, a study based on its optimization is developed. Main emphasis is given to the sequence and subsequent number of steps involved in the backwash. The ultimate goal is thus to increase the availability and recovery of the process while still attaining a high cleaning effect during the backwash. This optimization is done through the realization of various experiments using DOW™ Ultrafiltration SFP-2660 outside-in polyvinylidene difluoride (PVDF) membranes following an exhaustively planned factorial design of experiments. The factors being assessed are the steps normally performed during a backwash. These are the air scour (AS/D), the draining (D), the backwash top (BWT) with or without air scour, the backwash bottom (BWB) and the forward flush...

Active Composite Polymeric Membranes for the Separation of Nd(III)

Abstract Active composite polymeric membranes were prepared in order to improve the lifetime of supported liquid membranes (SLM) for the separation of Nd(III). The aim of the paper was to demonstrate the applicability of these type of composite membranes, based on two layer of polysulfone (PSf) and polyamide (PA), for metal transport. Thus, the membrane characterization, the influence of the carrier concentration in the transport, and the stability of the membranes have been studied. The results obtained are quite satisfactory, both from the standpoint of transport ability and stability. The need for an efficient carrier has been demonstrated and its influence reported. In addition, a preliminary investigation of the transport mechanism has been performed.

Effect of Pectinase Immobilization in a Polymeric Membrane on Ultrafiltration of Fluid Foods

The aim of this research was to obtain an enzymatic membrane reactor for use to clarify a model system and apple juice with a 12% soluble solid content and 1 mg/mL of pectin by water-soluble pectinolytic enzymes which were immobilized on polysulfone membranes. These membranes were synthesized in the laboratory by immersion precipitation (phase inversion) from polysulfone with and without active carbon. To ensure the cut-off separation of the membrane in the ultrafiltration process a commercial flat membrane with an 8-kDa molecular weight cut-off was used. The influence of different parameters (viscosity, density, reducing sugars, color, pH, and presence of pectin) on the initial sample and the volumetric permeate flux was also evaluated. The obtained membranes were characterized physically using a scanning electron microscopy SEM and analyses were performed with IFME® software. The results indicated that immobilization of the enzyme in the membrane allowed an interaction between the recirculating sample and the membrane, the one obtained with activated carbon and immobilized enzymes showed higher degradation of pectin, improving the performance of the volumetric permeate flux.

Atmospheric CO2 capture for the artificial photosynthetic system

The aim of these studies is to evaluate the ambient CO2 capture abilities of the membrane contactor system in the same conditions as leafs, such as ambient temperature, pressure and low CO2 concentration, where the only driving force is the concentration gradient. The polysulfone membrane employed was made by a phase inversion process and characterized by ESEM micrographs which were used to determine the thickness, asymmetry and pore size. Besides, the porosity of the membrane was measured from the membrane and polysulfone density correlation and the hydrophobicity was analyzed by contact angle measurements. Moreover, the compatibility of membrane and absorbent was evaluated, in order to exclude wetting issues by meaning of swelling, dynamic contact angle and AFM analysis. The prepared membranes were introduced into a cross flow module and used as contactors between CO2 and the absorbing media, a potassium hydroxide solution. The influence of the membrane thickness, absorbent stirring rate, solution pH and absorption time on CO2 capture were evaluated. Absorbent solution stirring rate showed no statistically significant influence on absorption. We observed a non-linear correlation between the capture rate and the increase of absorbent solution pH as well as absorption time. The results showed that the efficiency of our CO2 capture system is similar to stomatal carbon dioxide assimilation rate, achieving stable value of 20μmol/m2·s after 1h of experiment.

Membrane contactors for CO2 capture processes – critical review

Abstract The use of membrane contactor in industrial processes is wide, and lately it started to be used in CO2 capture process mainly for gas purification or to reduce the emission. Use of the membrane contactor provides high contact surface area so the size of the absorber unit significantly decreases, which is an important factor for commercialization. The research has been caried out regarding the use of novel materials for the membrane production and absorbent solution improvements. The present review reveals the progress in membrane contactor systems for CO2 capture processes concerning solution for ceramic membrane wetting, comparison study of different polymers used for fabrication and methods of enzyme immobilization for biocomposite membrane. Also information about variety of absorbent solutions is described.

Method for distinguishing between abiotic organic and biological fouling of reverse osmosis elements used to treat wastewater

aDow Water & Process Solutions, Dow Chemical Ibérica S.L., Tarragona 43006, Spain, email: gmassons@dow.com (G. Massons-Gassol), ggilabertoriol@dow.com (G. Gilabert-Oriol), vgomez2@dow.com (V. Gomez), vgarciamolina@dow.com (V.G. Molina) bDepartament d’ Enginyeria Química, Universitat Rovirai Virgili, Tarragona 43007, Spain, email: ricard.garcia@urv.cat cDow Water & Process Solutions, FilmTec Corporation, Edina 55439, USA, email: arrowotl@dow.com

Characterization of Carbon Molecular Sieve Membranes Supported on Ceramic Tubes

Carbon molecular sieve membranes have been analyzed in supported and unsupported configurations in this experimental study. The membranes were used to adsorb CO2, N2 and CH4, and their adsorption data were analyzed to establish differences in rate and capacity of adsorption between the two types of samples (supported and unsupported). Experimental results show an important effect of the support, which can be considered as an additional parameter to tailor pore size on these carbon membranes. Immersion calorimetry values were measured by immersing the membranes into liquids of different molecular dimensions (dichloromethane, benzene, n-hexane, 2,2-dimethylbutane). Similarities were found between adsorption and calorimetric analysis. The pore volume of the samples analyzed ranged from 0.016 to 0.263 cm3/g. The effect of the pyrolysis temperature, either 550 or 700 °C, under N2 atmosphere was also analyzed. Quantification of the pore-size distribution of the support was done by liquid–liquid displacement porosimetry. The composite membrane was used for CO2/CH4 separation before and after pore plugging was done. The ideal selectivity factors value (4.47) was over the Knudsen theoretical factor (0.60) for membrane pyrolyzed at 600 °C, which indicates the potential application of these membranes for the separation of low-molecular weight gases.